About This Page
This is a clinician-written, evidence-based guide aligned to the MCC Examination Objectives. It is structured by clinical presentation — the way the MCCQE tests and the way patients actually present. Management reflects current Canadian guidelines (CMA, CFPC, CPS). Always cross-reference with institutional protocols and clinical judgment.
The Bottom Line
- Differentiate TB infection from active TB disease: TST/IGRA can support infection but cannot rule out active disease
- Suspected infectious pulmonary TB requires airborne precautions, public health notification and sputum AFB smear/culture/NAAT
- Risk assessment is central in Canada: contact, high-incidence settings, homelessness, incarceration, HIV, transplant and TNF-alpha inhibitors
- Treatment of active TB is multi-drug and public-health coordinated
- TB is a CanMEDS presentation: confidentiality, stigma, adherence, contact tracing, cultural safety and public health obligations matter
Approach to the Presentation
Tuberculosis in Canada requires a structured distinction between screening, latent TB infection and active TB disease. The Canadian Tuberculosis Standards provide the national reference for prevention, diagnosis and management. Ask why TB is being considered: exposure/contact tracing, pre-immunosuppression screening, immigration/occupational screening, symptoms, abnormal imaging or extrapulmonary disease. Suspected pulmonary or laryngeal TB is potentially infectious and should trigger airborne precautions and public health involvement while microbiologic testing is arranged.
Differential Diagnosis
| diagnosis | likelihood | key features | distinguishing test |
|---|---|---|---|
| Active pulmonary tuberculosis | must-not-miss | Chronic cough, fever, night sweats, weight loss, haemoptysis, exposure risk, upper-lobe or cavitary disease | Sputum AFB smear/culture and NAAT; CXR/CT supports but culture confirms |
| Extrapulmonary tuberculosis | must-not-miss | Lymphadenitis, pleural effusion, meningitis, bone/spine pain, abdominal symptoms or genitourinary symptoms | Site-specific imaging and specimen for AFB smear/culture/NAAT/histology |
| TB meningitis | must-not-miss | Subacute headache, fever, meningism, cranial nerve palsies, confusion and hydrocephalus risk | CSF lymphocytic pleocytosis, low glucose, high protein, AFB culture/NAAT; urgent specialist treatment |
| Latent tuberculosis infection | common | Asymptomatic person with exposure or risk factor; normal exam and no active disease symptoms | Positive TST or IGRA after active disease excluded clinically and radiographically |
| Community-acquired pneumonia | common | Acute fever, cough, sputum, pleuritic pain and focal consolidation; shorter course than TB | CXR and clinical response to appropriate therapy |
| Nontuberculous mycobacterial disease | less common | Chronic cough, bronchiectasis/COPD, nodular disease, cavitation; environmental exposure | Repeated sputum cultures meeting diagnostic criteria and species identification |
| Lung cancer | less common | Weight loss, cough, haemoptysis, smoking history and mass lesion | CT chest and tissue diagnosis |
| Sarcoidosis | less common | Bilateral hilar lymphadenopathy, cough, erythema nodosum or uveitis | Imaging and biopsy showing non-caseating granulomas after infection excluded |
| Fungal infection | rare | Cavitary or nodular lung disease, travel/exposure or immunocompromise | Fungal culture/serology/antigen or tissue diagnosis |
Red Flags & Key History
Symptoms
Cough >2-3 weeks with fever, night sweats, weight loss or haemoptysis
Close contact with infectious TB or residence/birth in high-incidence setting
HIV, transplant, TNF-alpha inhibitor, dialysis, silicosis, diabetes, undernutrition or corticosteroid exposure
Neurological symptoms with TB risk — TB meningitis is time-critical
Pre-biologic or transplant screening — exclude active disease before treating latent TB
Ask about prior TB treatment, BCG vaccination, previous TST/IGRA and drug-resistance exposure
Signs
Cachexia, fever, lymphadenopathy, crackles or signs of pleural effusion
Meningism, cranial nerve palsy or altered mental status
Spinal tenderness or neurological signs suggesting Pott disease/epidural involvement
Airborne infection risk: coughing patient with suspected pulmonary/laryngeal TB
Approach to Investigation
First-line
Chest X-rayInitial imaging for pulmonary symptoms, positive screening test, contact evaluation or pre-immunosuppression assessment
Sputum AFB smear and cultureUsually multiple specimens; culture is essential for confirmation and drug susceptibility
NAAT for Mycobacterium tuberculosis complexSupports rapid diagnosis and may identify rifampin resistance depending on assay
TST or IGRABoth are acceptable for TB infection diagnosis in Canadian Standards; choose based on context
HIV testingRecommended when TB is suspected or diagnosed because co-infection changes management
Second-line
CT chestWhen CXR is equivocal, complications suspected or detailed assessment is needed
Drug susceptibility testingRequired for culture-positive TB to guide regimen and resistance management
Site-specific biopsy/aspirateFor lymph node, pleural, bone, CNS, abdominal or genitourinary TB
Baseline treatment labsCBC, liver enzymes, bilirubin, creatinine, hepatitis/HIV testing and medication review before therapy
Specialist
Public health / TB clinic referralActive TB and many latent TB decisions are coordinated through public health/TB programmes
Infectious diseases / respirologyDrug resistance, HIV coinfection, pregnancy, pediatrics, liver disease, extrapulmonary disease or intolerance
Management Principles
Canadian Tuberculosis Standards, 8th edition1
Suspected active pulmonary TB
- Place under airborne precautions in healthcare settings
- Notify public health according to provincial/territorial requirements
- Obtain sputum AFB smear/culture and NAAT; do not rely on TST/IGRA to rule out active TB
- Avoid fluoroquinolone monotherapy when TB is possible because it can delay diagnosis
2
Active TB treatment principles
- Use multi-drug therapy with public health/TB specialist oversight
- Assess drug susceptibility, adherence supports, interactions and toxicity monitoring
- Coordinate contact tracing and directly observed or directly supported therapy where indicated
3
Latent TB infection
- Diagnose only after active TB disease is excluded
- Offer treatment when risk of progression justifies therapy, especially contacts and patients before immunosuppression
- Choose regimen through public health/local TB clinic considering interactions, hepatotoxicity and adherence
4
Equity and communication
- Use culturally safe communication and professional interpreters
- Address stigma, housing, immigration fears, income barriers and adherence supports without judgement
Complications & Pitfalls
- TST/IGRA misuse: These tests support TB infection diagnosis but do not rule out active TB.
- No isolation: Suspected infectious pulmonary TB requires airborne precautions before diagnostic certainty.
- Single-drug error: Latent TB regimens must never be used when active TB is possible.
- Culture omission: Culture and susceptibility are essential.
- Fluoroquinolone masking: Empiric fluoroquinolones can delay TB diagnosis.
MCCQE1 Exam Tips
- 1Latent infection is asymptomatic with positive TST/IGRA after active disease excluded; active disease needs microbiology and public health action
- 2Suspected pulmonary TB = airborne precautions + sputum AFB/culture/NAAT + public health notification
- 3A positive TST after BCG is interpreted based on risk, timing and Canadian Standards
- 4Before TNF-alpha inhibitors, screen for latent TB and treat if indicated after active disease is excluded
- 5TB meningitis is a must-not-miss cause of subacute meningitis
- 6Contact tracing, adherence support and cultural safety are testable CanMEDS components
practicetest your knowledge on tuberculosis — screening, diagnosis & management (canadian approach)Apply what you've learnt with MCCQE1-style questions from the iatroX Q-Bank — infectious disease and beyond.
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